1. Field
This application generally relates to an apparatus and method for wastewater treatment and more specifically to an apparatus and method incorporating natural systems for treatment and management of agricultural animal wastewater.
2. Prior Art
Agricultural animal waste disposal is a major problem. Over the past several decades, increased demand for meat and dairy products has facilitated the rapid growth of the commercial livestock industry. The increased demand and subsequent growth of the industry has led to the utilization of more centralized higher capacity farming operations. These farming operations are sometimes referred to as concentrated animal feeding operations (CAFO's). While these CAFO's may be more productive and cost efficient, they come with the down side of manure management issues. As the commercial livestock industries use of CAFO's has increased, so has environmental concerns over the impact their manure waste has on water and air quality.
Environmental concerns over manure waste from CAFO's are especially pronounced for CAFO's that produce liquid manure waste that is treated and managed using lagoon-spray field systems. Lagoon-spray field systems are systems that generally treat liquid manure waste in large anaerobic lagoons and then intermittently dispose of it through land applications. This system was developed in the early and mid twentieth century prior to the current trend in high concentrated livestock operations. As the livestock industry has expanded, treatment of liquid manure waste using lagoon-spray field systems has come under increased public and governmental scrutiny due to environmental concerns over leaks, spills, odors, and ammonia emissions from the anaerobic lagoons as well as the high nutrient content of the lagoon effluent that is applied to spray fields. Lagoon effluent often contains high levels of biochemical oxygen demand (BOD), Nitrogen (N), and Phosphorus (P) that cannot be decreased to acceptable levels by anaerobic treatment alone. In recent years, States and Federal agencies have promulgated strict rules and regulations governing lagoon-spray field systems in agricultural operations. In some cases, moratoriums on the use or permitting of new lagoon-spray field systems have been enacted.
The swine farming industry in North Carolina is a great example of a commercial livestock industry that has migrated to the use of CAFO's over the past several decades and still primarily uses lagoon-spray field systems to treat and manage liquid manure waste. In 1998 the State of North Carolina enacted a moratorium that prevented the construction and permitting of new lagoon-spray field systems until an environmentally superior waste management technology or process could be developed. In 2000 and 2002, the Attorney General of North Carolina entered into agreements with private companies to promote the identification and development of environmentally superior waste management technologies for use on North Carolina swine farms owned by the companies. This agreement is commonly referred to as the “Smithfield Agreement”. The Smithfield Agreement defines an environmentally superior technology (EST) as any technology, or combination of technologies that:                1. is permittable by the appropriate governmental authority,        2. is determined to be technically, operationally and economically feasible for an identified category or categories of farms as described in the agreements, and        3. meets the following performance standards:                    a) Eliminates the discharge of animal waste to surface waters and groundwater through direct discharge, seepage or runoff,            b) Substantially eliminates atmospheric emissions of ammonia,            c) Substantially eliminates the emission of odor that is detectable beyond the boundaries of the parcel or tract of land on which the swine farm is located,            d) Substantially eliminates the release of disease-transmitting vectors and airborne pathogens, and            e) Substantially eliminates nutrient and heavy metal contamination of soil and groundwater.These basic requirements for an EST are also codified in North Carolina Administrative Code 15A NCAC 02T.1307—Swine Waste Management System Performance Standards and by proxy in 15A NCAC 02T.1308—Evaluation and Approval of Swine Waste Management Systems. Several of the EST candidates evaluated under the Smithfield Agreement are listed below:                        1. Solids Separation/Nitrification-Denitrification/Soluble Phosphorus Removal/Solids Processing System (U.S. Pat. No. 6,893,567).        2. ORBIT—High Solids Anaerobic Digester.        3. Ambient Temperature Anaerobic Digester and Greenhouse for Swine Waste Treatment and Bioresource Recovery.        4. Solids Separation-Reciprocating Wetland.        5. Ekokan Upflow Biofilter.        6. Belt Manure Removal and Gasification System to Convert Dry Manure Thermally to a Combustible Gas Stream for Liquid Fuel Recovery.        7. Solids Separation/Combustion for Energy and Ash Recovery.        8. Solids Separation/Constructed Wetlands System.        9. Sequencing Batch Reactor.        10. Manure Solids Conversion to Insect Biomass—Black Soldier Fly Project.        11. ISSUES—Innovative Sustainable Systems Utilizing Economical Solutions.        
Although considerable time, money, and effort has been put towards developing an EST in North Carolina, an EST candidate has yet to be developed or identified that meets the definition of an EST, nor has a candidate reached permittable status. As a result, in 2007 with the passing of Senate Bill 1465, the State of North Carolina converted what had been a temporary 10 year moratorium on lagoon-spray field systems into a permanent moratorium. This has permanently curtailed the growth of the industry in North Carolina until a solution to the problem is found.
While the lagoon-spray field system problem and well defined requirements for a solution described here are specific to North Carolina, the problem and its solution are applicable far beyond the boarders of North Carolina. The situation in North Carolina is simply a microcosm of the broader manure management problem the commercial livestock industry is facing across the United States. In addition to the EST candidates evaluated under the Smithfield Agreement listed above, the following are additional prior art examples of efforts to improve agricultural animal waste treatment with similar disadvantages; U.S. Pat. No. 4,432,869 (Groeneweg et al.), U.S. Pat. No. 5,078,882 (Northrop), U.S. Pat. No. 5,135,659 (Wartanessian), U.S. Pat. No. 5,137,625 (Wolverton), U.S. Pat. No. 5,200,082 (Olsen et al.), U.S. Pat. No. 5,545,560 (Chang), U.S. Pat. No. 5,863,434 (Masse et al.), U.S. Pat. No. 5,885,461 (Tetrault et al.), U.S. Pat. No. 6,083,386 (Lloyd), U.S. Pat. No. 6,113,788 (Molof et al.), U.S. Pat. No. 6,139,743 (Park et al.), U.S. Pat. No. 6,190,566 (Kolber), U.S. Pat. No. 6,284,054 (Galvin), U.S. Pat. No. 7,001,512 (Newsome), U.S. Pat. No. 7,279,104 (Keeton, Jr.), U.S. Pat. No. 7,422,680 (Sheets, Sr.), U.S. Pat. No. 7,481,935 (Olivier)
One of the main problems with many of the prior art examples listed above and the industries approach to the problem in general is that the focus has tended to be on technologies and processes that are more appropriate for large scale waste treatment operations. e.g. solids separation, aeration, heating etc. While CAFO's are by name “concentrated”, the volume of wastewater they produce is rather decentralized as compared to advanced wastewater treatment facilities that take advantage of economies of scale. Waste treatment technologies that can meet the “technically feasible” requirements of an EST have existed for years but are too expensive and complicated to construct and operate at the farm level. They are expensive to build, are too complicated operate without significant oversight, and have high energy requirements. The key to solving the problem lies in finding an adequate treatment process that is also “economically and operationally feasible” for the farmer and commercial livestock industry. This thought is echoed by the following statement on the North Carolina State University College of Agriculture and Life Sciences' Smithfield Agreement website: “The swine industry is an important part of North Carolina's economy. The alternative waste management technologies being evaluated are designed not only to treat waste in a manner that protects the environment but also to treat waste in an economically feasible manner that allows the swine industry to survive” [6].
Another problem with many of the prior art examples listed above, and the industries approach to the problem in general is that they have tended to focus on year round treatment of waste. Treatment systems utilizing year round treatment and frequent or continuous discharge are more difficult to permit as the regulatory community less likely to permit a treatment system where there is little opportunity for management and oversight of the discharges. Year round treatment is especially problematic for treatment systems that employ predominantly natural systems for waste treatment (e.g. wetlands) due to the fact that the winter temperatures experienced for most of the United States have a negative effect on their operation. While all waste treatment methods rely on natural responses such as gravity for sedimentation or natural components such as biological organisms, a natural system for waste treatment depends primarily on its natural components to achieve the intended purpose. A natural system might typically include pumps and piping for waste conveyance but would not depend on external energy sources exclusively to maintain the major treatment responses [5]. As such, a natural system (or systems) for waste treatment has an advantage in that it would cost less to build, is easy to operate, and requires less energy. However, these natural systems have not proved to be an adequate solution to the problem because of reduced effectiveness during the colder winter months.
Specifically, many of the prior art examples listed above have one or more of the following problems:                1. they employ a considerable amount of new infrastructure or equipment with moving parts which results in the upfront capital costs being too high to be economically feasible,        2. they have high operational energy requirements which prevents them from being operationally or economically feasible,        3. they are often just too complicated for the average farmer to operate without significant oversight which prevents them from being operationally feasible,        4. natural systems that could be operationally and economically superior have reduced effectiveness during the colder months of the year which prevents them from being technically feasible.        
While various systems have been developed for treating agricultural animal wastewater, including the EST candidates and prior art listed above, there still remains a need in the art for a technically, operationally, and economically feasible agricultural animal wastewater treatment system that costs less to build, is easier to understand and operate, and requires little energy input. A method based primarily on natural systems for agricultural animal wastewater treatment has the best chance for succeeding as these systems require less equipment with moving parts, have low operational energy requirements, and are simple for farmers to understand and use.